Jet sprayer actuated by supersonic waves



`lune 27, 1950 c. w. HANsELL JET SPRAYER ACTUATED BY sUPERsoNIc wAvEsFiled April l, 1946 TSV A -wir m T. NW E Vf Nc JN. k A

ATTORN EY Patented June 27, 1950 JET SPRAYEB ACTUATED BY SUPEBSONICWAVES Clarence W. Hansell, Port Jederson, N. Y., as-

signor to Radio Corporation poration ot Delaware of America, a cor-Appuuon apra 1, 194s, semi No. 658,850 1s claims. (ci. :i1-1s)vibrational waves strike an exposed surface 0f the liquid.

'I'he sprayer is applicable to facsimile recording and to variouspainting and spraying operations, and is particularly suited toperforming the same operations as the device called an air brush. whichis now used by many commercial artists. It is suitable for performingmany striping and ilnishing operations in industry, and. in general, itmay be used to control the ilow of liquids in many advantageous ways.

It has been demonstrated by R. W. Wood and A. L. Loomis that waves froma piezo-electric quartz crystal exert a unidirectional pressure whenthey arrive at the surface of a liquid. In one experiment in which acrystal was vibrated in oil they reported that a mound was raised on thesurface of the oil up to a height of '1 centimeters (see TheEncyclopaedia Britannica. 14th edition, vol. 21, page 12, and theadditional reference cited there).

To explain how supersonic waves exert such a large radiation pressurewhen they strike the surface of a liquid it may be noted that,generally, ,liquids will stand any reasonable amount of pressure butthey cannot take any substantial tension because they vaporize to formvoids which relieve the tension. Since the supersonic waves in a uniformliquid cause equal increase and decrease in pressure at time periods ahalf cycle apart in time, or a half wave diilerent in position, in thedirection of travel of the waves, it follows that the liquid must beunder a steady state pressure about equal to, or greater than, theamount of peak decrease in pressure due to the waves if voids are not tobe formed in the liquid.

Under conditions such that the waves are 4directed toward an exposedsurface of the liquid the region in the liquid at and near the surfacemay not be under sumcient pressure to equal the decrease in pressure atthe peak of the negative cycles of the supersonic waves. As aconsequence the push of the positive halves of the waves toward thesurface cannot be balanced by any corresponding counter pressure on thenegative halves of the waves. The only restoring force to balance thepositive half cycles of pressure is that exerted by the air less thevapor pressure of the liquid in the inevitable voids formed in theliquid on the negative half cycles of pressure. This restoring force isrelatively small and may be far below the positive forward force of thewaves.

The overall result of this phenomenon is that strong supersonic motionsor waves in a liquid. as the waves arrive at an exposed surface, arerectiiled or converted into unidirectional motions up out of the mainbody of the liquid. Thus supersonic waves may be used to causeunidirectional ilow of liquids and, by modulating the strength of thewaves ywe may modulate the unidirectional ilow.

'Ihe experiment of Wood and Loomis, in which supersonic waves raised amound '1 centimeters high on the surface of a liquid was done with theconcentration ot vibrational waves which exist in a free liquid at alittle distance from the surface of a strongly oscillating crystal. Ifthe liquid, instead of being in an open vessel is conilned in a taperedcontainer or nozzle having the vibrating crystal at the large end andbeing open to the air at the small end, then the intensity of the wavesat the open tip of the nozzle may be made much greater than theintensity of the waves at the crystal. Thus, by means of a taperedcolumn of liquid carrying supersonic waves from the large to the smallend it is possible to provide for very intense waves at the small end,which are capable of causing very large unidirectional velocities ofliquid thrown out of the small end. For this intensity of ultrasonicradiation Ludwig Bergmann, on page 45 of his book Ultrasonics (Wiley),gives calculations showing that when wave velocities in the liquid are1484 meters per second. the wave causes plus and minus alternations inpressure having a peak value ot 5.4x (l0)l dynes per square centimeter(about 80 pounds per square inch) and plus and minus peak velocities ofthe liquid of 36.7 centimeters per second. The accelerations in theliquid due to the waves are 100,000 times greater than the accelerationdue to gravity.

If the tapered liquid column varies in cross sectional area by somethinggreater than 100 to l, so as to result in a 100 to 1 increase in powerintensity of the waves in spite of power losses, then the above guresfor peak vibrational pressure, velocity and acceleration will all beincreased by 10 to 1. Therefore, if the liquid could remain free fromvoids, portions of the surface of the liquid would experienceaccelerations 1,000,000 times the acceleration due to gravity.

In practice voids will develop for some distance, extending through thesurface, but the liquid will be propelled at high velocity out of thetip of the nozzle. It may then be allowed to impinge upon a surfacewhich is moving with respect to the nozzle tip, to form a coating onlthe surface, the density of which may be modulated by modulating theintensity of the supersonic waves.

'I'he nozzle may be manipulated by an artist, similar to the manner ofusing the artists air brush, or -the relative motion may be performed ina facsimile recorder, or some form of painting machine. g g 4 As to therate at which the sprayer may be modulated, it maybe noted that in apaper appearing in Proc. I. R. E. for August 1939, J. Seiger describesthe Scophony system of television repiezo-electric crystal devicecomposed of a crystal element 3, electrodes I for exciting the crystaland two mechanical vibration transmitting media 5 which may be in theform of layers of suitable ception in which supersonic waves in a liquidare used to operate a light valve. Seiger reported that, by usingsupersonic waves in water, atl8 megacycles, and by using selective sideband fast enough for television. Y

The foregoing paragraphs deal largely with the background of art towhich my invention relates. As to the invention itself. the principalobjects are as follows:

a. To provide novel apparatus for the spraying of liquids in a line jet,or train of globules in response to the force of ejection from a nozzlewhich is produced by supersonic vibrational waves striking an exposedsurface of the liquid.

b. To provide means for the spraying of ink upon a recording surface inaccordance with the modulation of signals of the vibratorycharacteristics of a. piezo-electric crystal. where pressure is exertedupon a surface of the ink by a compressional wave which the crystalemits.

c. To provide paint spraying equipment of the type which utilizes theforce of supersonic waves for producing a jet.

d. To provide means acting upon a liquid to .produce supersoniccompressional waves therein.

whereby the liquid may be forced throughA an Vorice and come out as ajet or spray in consev'quence of the inherent characteristicy of the-compressional wave phenomenon to cause univ directional iiow of theliquid.

The foregoing and other objects and advantages of my invention will bestbe understood by r-the" following detailed description taken in view yoftheaccompanying drawings, wherein:

Fig.- 1 shows, moreor less diagrammatically, an arrangement of a liquidcontainer having one portion thereof conically walled and having anoriiice at the apex of the cone for the emission oi a liquid jet ortrain of globules as produced by a supersonic compressional wave appliedto a surface of the liquid:

Fig. 2 shows a modiiied shape for thewalls of the liquid container:

Fig. 3 shows a liquid container of still different shape and having inassociation therewith a solid cone which is capable of transmitting asupersonic wave to the liquid at a focal point opposite an orice in theliquid container soas to cause expulsion at right angles to the plane offeed of the liquid; and

Fig. 4 shows still another modification characterized by the use of asolid cone having a channel on its top side, down which the uid may befed to the apex of the cone, this apex being axially disposed withrespect to a nozzle. so as to cause a jet to be thrown out in responseto supersonic waves transmitted within the body of the cone.

Referring ilrst to Fig. 1, I show therein a container l having conicalwalls and an -orice 2 from which a iet or 'train of globules may beejected. At the base of the cone, I provide a material to offerimpedance matching for oscillations, such as to provide a broad band offrequency response.

' On the opposite side of the crystal 3 with respect to the conicalliquid container, I preferably dispose a second container 6 which isused to enclose a liquid preferably of the same characteristics as theliquid to be used in the jet. Within the container 6, I also provide aconical member 1 which acts as a supersonic wave reflecting andabsorbing cone and assists in matching the impedances to which thepiezo-electric device is subjected, thereby providing a broad band oifrequency response.

The container 6 has a illler hole which may be closed by means of ascrew plug 8. The container 6 also is formed with a flange 9 by means ofwhich it can be held tightly against the piezoelectric device 3, using ascrew cap l0 of insulating material which is screwed on to a. threadedend of a metal ring Il. The container B and the ring I I areelectrically connected respectively to one and the other of twoelectrodes 4 which are disposed on opposite faces of the crystal. Asource of high frequency energy i2 is coupled or connected to theelectrodes 4 through conductors i3 for activating the crystal. Ifdesired, this source may be modulated by signals thereby to producevariations in the amplitude of vthe mechanical vibrations set up in thecrystal. These vibrations are mechanically transmitted to the liquidswithin the two containers i and The liquid in the container i may bereplenished by means of a reservoir i4 containing as much liquid as maybe needed for operation of the device during a predetermined period oftime. The reservoir lli communicates with the container l by means of atube I5.

In the design of apparatus according to the foregoing description ofFig. 1, I have taken advantage of the teachings set forth in BritishPatent 466,212 filed by Scophouy Ltd. and J. H. Jefree wherein thefollowing is stated:

It is known to generate supersonic waves in liquids by means oi' piezoelectrically prosaid frequency in the crystal substance, or an oddmultiple of half the wave length.

This British patent does not, however, disclose the specific means whichI have found to be advantageous for matching the impedances of thevibratory media on the two sides of the crystal. By virtue of theseimprovements of design the device is rendered operative at much highmodulation frequencies than was heretofore found possible. In fact theapparatus of my invention may be used for responding to modulatedsupersonic waves and for recording conventional television signals on arecord sheet. My invention is, however, not limited to such use, but maybe employed in facsimile recording at any desired speed and for othercommercial purposes as well.

Considering the requirements for television image recording, however, itmay be seen that if the velocity of the waves in the liquid is, 148,400centimeters per second (as has been found to be normal by previousexperimenters) and if the frequency of the waves is chosen to be14,840,000 cycles per second then the length of the waves will be 0.01centimeter (0.00394 inch) and this should be the approximate diameter ofdroplets as they are ejected from the nozzle. The rate be 14,840,000droplets per oonmy eubientimeter and the total flow should be at therate of 7.77 cubic centimeters per second At this rate the device wouldconsume liquid at the rate of or 7.4 gallons per hour. At televisionspeeds, recording '1.5 x 10 inch limages, this amount of liquid would bespread over 56,250 sq. feet. This yns corresponds to 7600 square feetper gallon; That much paint when evenly spread over that many squarefeet would be approximately .000 thick.

A monochrome picture would, however, require a smaller consumption ofliquid, considering that the white areas would remain unpainted.

For slower speed facsimile recording my invention provides forconstant-frequency-variable.

length-pulse-transmission of signals for producing pulses of supersonicwaves which are repeat- I ed at a constant rate but which are varied inamplitude and cause a varying amount of liquid.

to be ejected by each pulse.

It is further contemplated that in carrying out my invention I may use amodulation Irequency as high as 9 megacycles per second even though theconstant frequency of the piezo-electric excitation means (the carrierfrequency) is only 18 megacycles. In order to accomplish this result,however, I intend to use all the available expedients which are knownfor improving the response.

Assuming that the shortest pulses are allowed a squareness correspondingto the third harmonic, then we may say that the shortest pulses will bel/aoooooo second in length. For 100 lines per inch detail, in 7.5 x 10inch images, we need '750,000 impulses per image and for one image perminute we then need a pulse rate of per second. The shortest pulseswould then be 6 transparencies which are translated into signals may bereproduced on a record medium which travels with sumcient speed past theiet so as to form enlargements in black and white or any other colors. Acombination of colors may also be used by repeated scannings of therecording medium, a different color being used with each scanning. Inthis way it is possible to obtain copies of paintings with any degree ofchange in the dimensions. and to print wall paper, canvas, or to applyan image directly to a wall forv decorative purposes. The invention mayalso be used for spraying acids and chemicals for the etching ofprinting plates and for putting decorative designs on articles ofmanufacture.

Still another application of my invention is contemplated, as forexample, in the automatic control of small amounts of liquids where suchcontrol is required in certain chemical processes. For example, theinvention may be used to control the addition of iluorine and 'iodinesolutions to the water supply of public water systems. The output ofchemicals from the jet may be made to respond to the rate of flow ofwater at some point in the system, bymeansof suitable electricalmeasuring and electrical control systems.

lAs a matter of engineering design it is contemplated that an optimumdiameter of the orifice 2 will be chosen so as to obtain the necessarycapillary eiects which will prevent the bleeding of the container in theabsence of propulsion by the supersonic waves. This, however,

is a matter of engineering design and the merits .of the invention in noway depend upon such design other than to meet the requirements foroperability.

It desired the entire recording system may be enclosed in a largercontainer so as to be operated under greater than atmospheric pressure.For

example, if the overall pressure is raised to ive atmospheres then thesupersonic waves can create a maximum difference in pressure of iiveatmospheres, between the ink source and the inside ci the' nozzle tipwhere cavitation of the ink due to the supersonic waves reaches itsmaximum amount. In other words, themaximum force available to replacethe ink elected from the nozzle tips is always equal to the absolutepressure of the air in which the system is immersed, less the vaporpressure of the ink in the cavities created by the supersonic waves inthe nozzle tip.

In some cases I expect to add liquids of relatively high vapor pressureto the iluids used in the Jet. for the purpose of increasing thepressure in the cavities produced by the halt cycles of tension in theliquid, to thereby obtain an increased unidirectional pumping effect dueto cavitation.

I have found that very line droplets of liquid are slowed down from veryhigh to low velocities. due to friction. in a short distance in air. Toreduce this effect I may employ a very rapidly moving stream of-air,passing over and past the end of the nozzle and flowing in the directionin which it is desired that the droplets should go. 4By this means agreater spacing ybetween the end of the nozzle and the recordsurfacevmay be made possible.

Referring now to Fig. 2. I show therein a modiication in which thenozzle or orifice for the liquid container is surrounded by a containerwall i8 which is of a blunt nose formation. This shape is intended toaid in replacing the liquid thrown out by the supersonic waves.Advantage u is taken of the principle of the Venturi tube, a

characteristic of which is to produce a vacuum which aids in replacingliquid thrown out through the iet. r

The walls of the container 6 may Fbe of glass or other material having aglazed inner surface for reducing friction. The walls may also be waxedoutside to inhibit wetting or they may be made hydrophobic by treatmentwith vapor of methyl chlorosilicones in the presence of adsorbed water,as described by F. J. Norton in his paper Organo-Silicon Films. GeneralElectric Review. August 1944.v The inside walls may, however, be etched,if desired, to aid in wetting, for the purpose of reducing wavereflections at the interface .between the liquid and its container.

The modication shown in Fig. 3 includes a liquid container having wallsI1 and I8 between which the liquid flows inward radially toward theorifice 2. The expulsion of the liquid as a Jet is produced'lbysupersonic waves which are carried in a solid 'cone I9, the apex ofwhich is disposedin back ofthe orifice 2. The supersonic waves areapplied to the cone i9 in the same manner Yas is described above withrespect to the liquid inthe container i (Fig. l). The compressionalwaves in the solid material of the cone I9 are greatly increasedinrelative intensity at the apex of the cone `and-thus the expulsion oftheliquid is produced with increasedv force.

The modification shown in Fig. 4 is one in which a solid cone 20 isslotted or channeled on the top side, the channel being Vindicated at2l. In this arrangement the fluid iiows down the channel and isejectedat the apex of the cone. The cone itself carries the supersonic wavesand, due to the cavitation and the rectification effect herein abovementioned, the forward propulsion of the .liquid greatly exceeds theforce of the negative half cycles ofthe compressional waves.

I claim: q

l. Apparatus for the spraying' of a liquid in a fine jet, or train ofglobules, comprising a liquid container vhaving an vintake orifice and aspray nozzle, piezo-electric means for applying compressional waves to asurface of said liquid within said container, and means for focussingthe effects of said compressional waves on thatV part of the liquidwhich faces said orifice.'

2. Apparatus according to claim 1 including l means for modulating theoutput of liquid from sonic compressional waves on a surface of saidliquid, said waves having a front which is caused to travel along theaxis of said nozzle and which in turn causes ejection of the liquid'fromsaid nozzle.

4. Apparatus in accordance with claim 3 wherein said compressional waveproducing means comprises a piezo-electric device which is activated byan alternating current, and saidV means includes a member formechanically conducting the vibrations of said device to a surface ofthe liquid in said reservoir.

5. In a liquid jet producing device, a container for the liquid, saidcontainer having an intake openingand a tapered end which is oriced atits apexV to' provide an outletv having capillary characteristics,piezo-electric means for producing vibrations on a surface of saidliquid, said vi# brations having a compressional wave front which isdirected toward said apex andl which causes the liquid to be ejectedfrom said orice. 5 6. A device according to claim 5 characterized by ablunt-nosed formation of said apex.

7. A device according to claim 5 having the inner walls of saidcontainer composed of a material the surface of which is subject to"wetting by said liquid. y

8. A liquid jet producing device comprising a liquid container oppositewalls of which are suitably oriflced to provide an entrance and an exitrespectively, the orices being mutually opposed, a solid cone ofmaterial having a modulus of elasticity which is favorable for thetransmission of supersonic waves therein, said cone having its apexinserted in said entrance orice, means for producing mechanicalvibrations of supersonic frequency in said cone and in a direction suchthat a compressional wave travels along the axis of said cone toward itsapex, and a liquid liing said container and in contact with said apex,said liquid being subject to expulsion through said exit orifice.

9. A device according to claim 8 including a piezo-electric elementmechanically coupled to Said cone and means for causing saidpiezo-electric element to translate electrical energy into mechanicalenergy.

l0. A device according to claim 8 further characterized in that saidcone is channeled to provide a canal for the ow of liquid down its topside when its conical axis lies horizontally, said channel entering thecontainer.

` 11. In a liquid jet producing device, a shell for the liquid, saidshell having a nozzle portion at one end thereof and a cylindricalportion at the other end thereof, a. re-entrant conically shaped memberattached to the outer extremity of said cylindrical portion andcooperating therewith for conning a quantity of liquid, a piezo-electricdevice constituting a partition wall between the nozzle portion and thecylindrical portion of said shell, electrical means for vibrating saidpiezoelectric device, and means for continuously replenishing the liquidwhich is ejected from the nozzle portion of said shell, this means beingoperative in such manner that the inertias of the 50 liquids onoppositesides of said piezo-electric device are maintainedin balancedrelation.

l2. In a liquid jet producing device, a shell for confining the liquid,said shell having a-nozzle portion at the end of a front chamber and a55 liquid-confining portion constituting a rear chamber, apiezo-electric device forming a partition wall between the two chambers,electrical means for exciting the piezo-electric device thereby to setup compressional Waves in the 60 liquids within the two chambers,thereby to cause jet-expulsion of liquid through the nozzle portion ofsaid shell, and means for continuously replenishing the liquid in thefront chamber, this means being effective to maintain a mechanical 65impedance match with respect to the transmission of compressional wavesthrough the liquids confined by the two chambers.

13. Apparatus for spraying a liquid in a fine jet comprising a movablemember for retaining a re- 70v movable record sheet, a liquid containerhaving an intake orice and a spray nozzle positioned adjacent saidmovable member, an electrically excited piezo-electric device forcausing the transmission of compressional waves through the liquidcontained in said container to spray the l Q surface of said recordsheet. and pressure eham- Number The following references are of recordin the le of thisrpatent:

UNITED STATES PATENTS Number Name Date 1,306,985 Wimms June 17, 1919Bailey ,-V.-- May 23, 1922 Y Blakeney May 31, 1927 Y Shore Nov. 23. 1937Hansen JanflO, 1939 Oilner 1--..,-4. Huf. 14, 1939 Genschmer Mar. 21,1939 K immich Sept. 13, 1939 .Oilner Nov. 18, 1941

